Aramid is a very high performance material. There are two distinct groups: para-aramids are strong and resistant to penetration and cutting; and meta-aramids are prized for their superior resistance to heat and fire. They are commonly referred to by their trademark names. P-aramids include Kevlar, Twaron and Technora; and Nomex is an M-aramid. Production is very expensive, which limits applications somewhat – finer yarns are more expensive per kg and the cost of meta-aramid varies greatly.

It can be described as a type of nylon (PA), but rarely is, because its polymer structure is quite different. Nylon is aliphatic – the polymer chains are branched and only semi-organised. By contrast, aramid consists of an aromatic polymer structure (closed rings of atoms), which produces a highly crystalline (oriented) structure. The strength of aramid is the result of inter-molecular hydrogen bonds between these long and highly oriented polymer chains, and the stacking of the aromatic structure. This is very different from the typical van der Waals interactions (weak molecular-level electrostatic attraction) found in regular plastics like nylon, which is the reason why they can be melt-processed at relatively low temperatures. Aramid does not melt and cannot be processed in the same way – it will eventually breakdown at around 450 degC – and therefore is only available as a spun fibre, or as part of a fibre-based composite.

Aside from all its benefits and life saving attributes, aramid has some weaknesses. It has much lower resilience compared to nylon and other plastic fibres, and repeated bending and flexing will cause the linear fibre structure to breakdown (fibrillate). It is also very vulnerable to UV degradation and must be protected from exposure to daylight.